Medical systems and methods

ABSTRACT

Tissue is resected and extracted from an interior location in a patient&#39;s body using a probe or tool which both effects resection and causes vaporization of a liquid or other fluid to propel the resected tissue through an extraction lumen of the resecting device. Resection is achieved using an electrosurgical electrode assembly including a first electrode on a resecting member and a second electrode within a resection probe or tool. Over a first resecting portion, radio frequency current helps resect the tissue and over a second or over transition region, the RF current initiates vaporization of the fluid or other liquid to propel the tissue from the resection device. In one embodiment, an extending element extends from a housing and into a channel in a resecting member as the resecting member moves toward a distal position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/292,711, filed Oct. 13, 2016, which is a continuation of U.S.application Ser. No. 14/053,434, filed Oct. 14, 2013, now U.S. Pat. No.9,498,244, which application claims the benefit of U.S. ProvisionalApplication No. 61/716,049, filed Oct. 19, 2012, the full disclosures ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to tissue resection devices and methods,for example, for use in resecting and extracting uterine fibroid tissue,polyps and other abnormal uterine tissue.

BACKGROUND OF THE INVENTION

Uterine fibroids are non-cancerous tumors that develop in the wall ofuterus. Such fibroids occur in a large percentage of the femalepopulation with some studies indicating up to 40 percent of all womenhave fibroids. Uterine fibroids can grow over time to be severalcentimeters in diameter and symptoms can include menorrhagia,reproductive dysfunction, pelvic pressure and pain.

One current treatment of fibroids is hysteroscopic resection ormyomectomy which involves transcervical access to the uterus with ahysteroscope together with insertion of a resecting instrument through aworking channel in the hysteroscope. The resecting instrument may be amechanical tissue cutter or an electrosurgical resection device such asan RF loop. Mechanical cutting devices are disclosed in U.S. Pat. Nos.7,226,459; 6,032,673 and 5,730,752 and U.S. Published Patent Appl.2009/0270898. An electrosurgical resecting device is disclosed in U.S.Pat. No. 5,906,615.

In a myomectomy or hysteroscopic resection, the initial step of theprocedure includes distention of the uterine cavity to create a workingspace for assisting viewing through the hysteroscope. In a relaxedstate, the uterine cavity collapses with the uterine walls in contactwith one another. A fluid management system is used to distend theuterus to provide a working space by means of a fluid being introducedthrough a passageway in the hysteroscope under sufficient pressure toexpand or distend the uterine cavity. The fluids used to distend theuterus are typically liquid aqueous solutions such as a saline solutionor a sugar-based aqueous solution.

While hysteroscopic resection can be effective in removing uterinefibroids, many commercially available instrument are too large indiameter and thus require anesthesia in an operating room environment.Conventional resectoscopes require cervical dilation to about 9 mm. Whatis needed is a system that can effectively resect and remove fibroidtissue through a small diameter hysteroscope.

SUMMARY OF THE INVENTION

The present invention provides methods for resecting and removing targettissue from a patient's body, such as fibroids from a uterus. The tissueis resected, captured in a probe, catheter, or other tissue-removaldevice, and expelled from the resecting device by vaporizing a liquidadjacent to the captured tissue in order to propel the tissue from thedevice, typically through an extraction or other lumen present in a bodyor shaft of the device. Exemplary embodiments of the tissue resectingdevice comprise an RF electrode, wherein the electrode can be advancedpast a tissue-receiving window on the device in order to sever a tissuestrip and capture the strip within an interior volume or receptacle onthe device. The liquid or other expandable fluid is also present in thedevice, and energy is applied to the fluid in order to cause rapidexpansion, e.g., vaporization, in order to propel the resected tissuestrip through the extraction lumen. In this way, the dimensions of theextraction lumen can be reduced, particularly in the distal regions ofthe device where size is of critical importance.

In another aspect of the invention, a tubular resecting device has aninner resecting sleeve that reciprocates in a passageway in an outersleeve or housing to resect tissue in a window of the outer sleeve.Within a distal portion of the stroke of the inner resecting sleeve, aprojecting element extends into a tissue extraction channel in the innersleeve. In a variation, the cross-section of the projecting elementfunctions in a scissor-like manner to push the tissue against anelectrode edge of the inner sleeve to resect the tissue. The projectingelement can have an axial length of at least 2 mm. The projectingelement also can have a tapered region for insuring that the innersleeve when moving distally is guided over the projecting element evenif there is flex in the distal portion of the outer sleeve in the regionof the tissue-receiving window.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of an assembly including a hysteroscope and atissue resecting device corresponding to the invention that is insertedthrough the working channel of the hysteroscope.

FIG. 2 is a schematic perspective view of a fluid management system usedfor distending the uterus and for assisting in electrosurgical tissueresection and extraction.

FIG. 3 is a cross-sectional view of the shaft of the hysteroscope ofFIG. 1 showing various channels therein.

FIG. 4 is a schematic side view of the working end of theelectrosurgical tissue resecting device of FIG. 1 showing an outersleeve, a reciprocating inner sleeve and an electrode arrangement.

FIG. 5 is a schematic perspective view of the working end of the innersleeve of FIG. 4 showing its electrode edge.

FIG. 6A is a schematic cut-away view of a portion of outer sleeve, innerRF resecting sleeve and a tissue-receiving window of the outer sleeve.

FIG. 6B is a schematic view of a distal end portion another embodimentof inner RF resecting sleeve.

FIG. 7A is a cross sectional view of the inner RF resecting sleeve ofFIG. 6B taken along line 7A-7A of FIG. 6B.

FIG. 7B is another cross sectional view of the inner RF resecting sleeveof FIG. 6B taken along line 7B-7B of FIG. 6B.

FIG. 8 is a schematic view of a distal end portion of another embodimentof inner RF resecting sleeve.

FIG. 9A is a cross sectional view of the RF resecting sleeve of FIG. 8taken along line 9A-9A of FIG. 8 .

FIG. 9B is a cross sectional view of the RF resecting sleeve of FIG. 8taken along line 9B-9B of FIG. 8 .

FIG. 10A is a perspective view of the working end of the tissueresecting device of FIG. 1 with the reciprocating RF resecting sleeve ina non-extended position.

FIG. 10B is a perspective view of the tissue resecting device of FIG. 1with the reciprocating RF resecting sleeve in a partially extendedposition.

FIG. 10C is a perspective view of the tissue resecting device of FIG. 1with the reciprocating RF resecting sleeve in a fully extended positionacross the tissue-receiving window.

FIG. 11A is a sectional view of the working end of the tissue resectingdevice of FIG. 10A with the reciprocating RF resecting sleeve in anon-extended position.

FIG. 11B is a sectional view of the working end of FIG. 10B with thereciprocating RF resecting sleeve in a partially extended position.

FIG. 11C is a sectional view of the working end of FIG. 10C with thereciprocating RF resecting sleeve in a fully extended position.

FIG. 12A is an enlarged sectional view of the working end of tissueresecting device of FIG. 11B with the reciprocating RF resecting sleevein a partially extended position showing the RF field in a first RF modeand plasma resection of tissue.

FIG. 12B is an enlarged sectional view of the working end of FIG. 11Cwith the reciprocating RF resecting sleeve almost fully extended andshowing the RF fields switching to a second RF mode from a first RF modeshown in FIG. 12A.

FIG. 12C is an enlarged sectional view of the working end of FIG. 11Cwith the reciprocating RF resecting sleeve again almost fully extendedand showing the explosive vaporization of a captured liquid volume toexpel resected tissue in the proximal direction.

FIG. 13 is an enlarged perspective view of a portion of the working endof FIG. 12C showing an interior chamber and a fluted projecting element.

FIG. 14 is a sectional view of the working end of FIG. 12C showing aninterior chamber and a variation of a projecting element.

FIG. 15 is a sectional view of the working end of FIG. 12C showing aninterior chamber and a variation of a projecting element configured toexplosively vaporize the captured liquid volume.

FIG. 16A is sectional view of a working end of a resection probe similarto that of FIGS. 11A-12C showing a variation of a projecting element andresecting sleeve.

FIG. 16B is another view of the working end of FIG. 16A with theresecting sleeve moving distally over a tapered portion of theprojecting element.

FIG. 17 is a schematic view of a system for fibroid removal including afluid management system.

FIG. 18 is a schematic view of the fluid management system of FIG. 17with an enlarged view of the working end of a tissue resecting probe asgenerally described in FIGS. 1-12C in a position to resect and remove afibroid.

FIG. 19 is a cut-away schematic view of a filter module of the fluidmanagement system of FIGS. 17-18 .

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an assembly that comprises an endoscope 50 used forhysteroscopy together with a tissue resecting and extracting device 100extending through a working channel 102 of the endoscope. The endoscopeor hysteroscope 50 has a handle 104 coupled to an elongated shaft 105having a diameter of 3 mm to 7 mm. The working channel 102 therein maybe round, D-shaped or any other suitable shape. The endoscope shaft 105is further configured with an optics channel 106 and one or more fluidinflow/outflow channels 108 a, 108 b (FIG. 3 ) that communicate withconnectors 110 a, 110 b configured for coupling to a fluid inflow source120, or optionally a negative pressure source 125 (FIGS. 1-2 ). Thefluid inflow source 120 is a component of a fluid management system 126as is known in the art (FIG. 2 ) which comprises a fluid container 128and pump mechanism 130 which pumps fluid through the hysteroscope 50into the uterine cavity. As can be seen in FIG. 2 , the fluid managementsystem 126 further includes the negative pressure source 125 coupled tothe tissue resecting device 100. The handle 104 of the endoscopeincludes the angled extension portion 132 with optics to which avideoscopic camera 135 can be operatively coupled. A light source 136 iscoupled to light coupling 138 on the handle of the hysteroscope 50. Theworking channel 102 of the hysteroscope is configured for insertion andmanipulation of the tissue resecting and extracting device 100, forexample to treat and remove fibroid tissue. In one embodiment, thehysteroscope shaft 105 has an axial length of 21 cm, and can comprise a0° scope, or 15° to 30° scope.

Still referring to FIG. 1 , the tissue resecting device 100 has a highlyelongated shaft assembly 140 configured to extend through the workingchannel 102 in the hysteroscope. A handle 142 of the tissue resectingdevice 100 is adapted for manipulating the electrosurgical working end145 of the device. In use, the handle 142 can be manipulated bothrotationally and axially, for example, to orient the working end 145 toresect targeted fibroid tissue. The tissue resecting device 100 hassubsystems coupled to its handle 142 to enable electrosurgical resectionof targeted tissue. A radiofrequency generator or RF source 150 andcontroller 155 are coupled to at least one RF electrode carried by theworking end 145 as will be described in detail below. In one embodimentshown in FIG. 1 , an electrical cable 156 and negative pressure source125 are operatively coupled to a connector 158 in handle 142. Theelectrical cable couples the RF source 150 to the electrosurgicalworking end 145. The negative pressure source 125 communicates with atissue-extraction channel 160 in the shaft assembly 140 of the tissueresecting device 100 (FIG. 4 ).

FIG. 1 further illustrates a seal housing 162 that carries a flexibleseal 164 within the hysteroscope handle 104 for sealing the shaft 140 ofthe tissue resecting device 100 in the working channel 102 to preventdistending fluid from escaping from a uterine cavity.

In one embodiment as shown in FIG. 1 , the handle 142 of tissueresecting device 100 includes a motor drive 165 for reciprocating orotherwise moving a resecting component of the electrosurgical workingend 145 as will be described below. The handle 142 optionally includesone or more actuator buttons 166 for actuating the device. In anotherembodiment, a footswitch can be used to operate the device. In oneembodiment, the system includes a switch or control mechanism to providea plurality of reciprocation speeds, for example 1 Hz, 2 Hz, 3 Hz, 4 Hzand up to 8 Hz. Further, the system can include a mechanism for movingand locking the reciprocating resecting sleeve in a non-extendedposition and in an extended position. Further, the system can include amechanism for actuating a single reciprocating stroke.

Referring to FIGS. 1 and 4 , an electrosurgical tissue resecting devicehas an elongate shaft assembly 140 extending about longitudinal axis 168comprising an exterior or first outer sleeve 170 with passageway orlumen 172 therein that accommodates a second or inner sleeve 175 thatcan reciprocate (and optionally rotate or oscillate) in lumen 172 toresect tissue as is known in that art. In one embodiment, thetissue-receiving window 176 in the outer sleeve 170 has an axial lengthranging between 10 mm and 30 mm and extends in a radial angle aboutouter sleeve 170 from about 45° to 210° relative to axis 168 of thesleeve. The outer and inner sleeves 170 and 175 can comprise a thin-wallstainless steel material and function as opposing polarity electrodes aswill be described in detail below. FIGS. 6A-8 illustrate insulativelayers carried by the outer and inner sleeves 170 and 175 to limit,control and/or prevent unwanted electrical current flows between certainportions of the sleeve. In one embodiment, a stainless steel outersleeve 170 has an O.D. of 0.143″ with an I.D. of 0.133″ and with aninner insulative layer (described below) the sleeve has a nominal I.D.of 0.125″. In this embodiment, the stainless steel inner sleeve 175 hasan O.D. of 0.120″ with an I.D. of 0.112″. The inner sleeve 175 with anouter insulative layer has a nominal O.D. of about 0.123″ to 0.124″ toreciprocate in lumen 172. In other embodiments, outer and or innersleeves can be fabricated of metal, plastic, ceramic of a combinationthereof. The cross-section of the sleeves can be round, oval or anyother suitable shape.

As can be seen in FIG. 4 , the distal end 177 of inner sleeve 175comprises a first polarity electrode with distal electrode edge 180about which plasma can be generated. The electrode edge 180 also can bedescribed as an active electrode during tissue resection since theelectrode edge 180 then has a substantially smaller surface area thanthe opposing polarity or return electrode. In one embodiment in FIG. 4 ,the exposed surfaces of outer sleeve 170 comprises the second polarityelectrode 185, which thus can be described as the return electrode sinceduring use such an electrode surface has a substantially larger surfacearea compared to the functionally exposed surface area of the activeelectrode edge 180.

In one aspect of the invention, the inner sleeve or resecting sleeve 175has an interior tissue extraction lumen 160 with first and secondinterior diameters that are adapted to electrosurgically resect tissuevolumes rapidly—and thereafter consistently extract the resected tissuestrips through the highly elongated lumen 160 without clogging. Nowreferring to FIGS. 5 and 6A, it can be seen that the inner sleeve 175has a first diameter portion 190A (with diameter A) that extends fromthe handle 142 (FIG. 1 ) to a distal region 192 of the sleeve 175wherein the tissue extraction lumen transitions to a smaller seconddiameter lumen 190B with a reduced diameter indicated at B which isdefined by the electrode sleeve element 195 that provides the resectionelectrode edge 180. The axial length C of the reduced cross-sectionlumen 190B can range from about 2 mm to 20 mm. In one embodiment, thefirst diameter A is 0.112″ and the second reduced diameter B is 0.100″.As shown in FIG. 5 , the inner sleeve 175 can be an electricallyconductive stainless steel and the reduced diameter electrode portionalso can comprise a stainless steel electrode sleeve element 195 that iswelded in place by weld 196 (FIG. 6A). In another alternativeembodiment, the electrode and reduced diameter electrode sleeve element195 comprises a tungsten tube that can be press fit into the distal end198 of inner sleeve 175. FIGS. 5 and 6A further illustrate theinterfacing insulation layers 202 and 204 carried by the first andsecond sleeves 170, 175, respectively. In FIG. 6A, the outer sleeve 170is lined with a thin-wall insulative material 200, such as PFA, oranother material described below. Similarly, the inner sleeve 175 has anexterior insulative layer 202. These coating materials can be lubriciousas well as electrically insulative to reduce friction duringreciprocation of the inner sleeve 175.

The insulative layers 200 and 202 described above can comprise alubricious, hydrophobic or hydrophilic polymeric material. For example,the material can comprise a bio-compatible material such as PFA,TEFLON®, polytetrafluroethylene (PTFE), FEP (Fluorinatedethylenepropylene), polyethylene, polyamide, ECTFE(Ethylenechlorotrifluoro-ethylene), ETFE, PVDF, polyvinyl chloride orsilicone.

Now turning to FIG. 6B, another variation of inner sleeve 175 isillustrated in a schematic view together with a tissue volume beingresected with the plasma electrode edge 180. In this embodiment, as inother embodiments in this disclosure, the RF source operates at selectedoperational parameters to create plasma around the edge 180 of electrodesleeve 195 as is known in the art. Thus, the plasma generated atelectrode edge 180 can ablate a path P in the tissue 220 and is suitedfor resecting fibroid tissue and other abnormal uterine tissue. In FIG.6B, the distal portion of the resecting sleeve 175 includes a ceramiccollar 222 which is proximate to the distal edge 180 of the electrodesleeve 195. The ceramic collar 222 functions to confine plasma formationabout the distal electrode edge 180 and functions further to preventplasma from contacting and damaging the polymer insulative layer 202 onthe resecting sleeve 175 during operation. In one aspect of theinvention, the path P ablated in the tissue 220 with the plasma atelectrode edge 180 provides a path P having an ablated width indicatedat W, wherein such path width W is substantially wide due to tissuevaporization. This vaporization of tissue in path P to provide theresection is substantially different than the effect of resectingsimilar tissue with a sharp blade edge, as in various prior art devices.A sharp blade edge can divide tissue (without cauterization) but appliesmechanical force to the tissue and may prevent a large cross sectionslug of tissue from being resected. In contrast, the plasma at theelectrode edge 180 can vaporize a path Pin tissue without applying anysubstantial force on the tissue to thus resect larger cross sections orstrips of tissue. Further, the plasma resecting effect reduces the crosssection of tissue strip 225 received in the reduced cross-section region190B of the tissue extraction lumen 160. FIG. 6B depicts a tissue strip225 entering the reduced cross-section region 190B, wherein the tissuestrip has a smaller cross-section than the lumen due to the vaporizationof tissue. Further, the cross section of tissue strip 225 as it entersthe larger cross-section lumen 190A results in even greater free space197 around the tissue strip 225. Thus, the resection of tissue with theplasma electrode edge 180, together with the lumen transition from thesmaller cross-section (190B) to the larger cross-section (190A) of thetissue-extraction lumen 160 can significantly reduce or eliminate thepotential for successive resected tissue strips 225 clogging the lumen.Prior art resection devices with such a small diameter tissue-extractionlumen typically have problems with tissue clogging.

In another aspect of the invention, the negative pressure source 125coupled to the proximal end of tissue-extraction lumen 160 (see FIGS. 1and 4 ) also assists in aspirating and moving tissue strips 225 in theproximal direction to a collection reservoir (not shown) outside thehandle 142 of the resecting device.

FIGS. 7A-7B illustrate the change in lumen diameter of resecting sleeve175 of FIG. 6B. FIG. 8 illustrates the distal end of a variation ofresecting sleeve 175′ which is configured with an electrode resectingelement 195′ that is partially tubular in contrast to the previouslydescribed tubular electrode element 195 (FIGS. 5 and 6A). FIGS. 9A-9Bagain illustrate the change in cross-section of the tissue-extractionlumen between reduced cross-section region 190B′ and the increasedcross-section region 190A′ of the resecting sleeve 175′ of FIG. 8 .Thus, the functionality remains the same whether the resecting electrodeelement 195′ is tubular or partly tubular. In FIG. 8A, the ceramiccollar 222′ is shown, in one variation, as extending only partiallyaround sleeve 175′ to cooperate with the radial angle of resectingelectrode element 195′. Further, the variation of FIG. 8 illustratesthat the ceramic collar 222′ has a larger outside diameter thaninsulative layer 202. Thus, friction may be reduced since the shortaxial length of the ceramic collar 222′ interfaces and slides againstthe interfacing insulative layer 200 about the inner surface of lumen172 of outer sleeve 170.

In general, one aspect of the invention comprises a tissue resecting andextracting device (FIGS. 10A-11C) that includes first and secondconcentric sleeves having an axis and wherein the second (inner) sleeve175 has an axially-extending tissue-extraction lumen therein, andwherein the second sleeve 175 is moveable between axially non-extendedand extended positions relative to a tissue-receiving window 176 infirst sleeve 170 to resect tissue, and wherein the tissue extractionlumen 160 has first and second cross-sections. The second sleeve 175 hasa distal end configured as a plasma electrode edge 180 to resect tissuedisposed in tissue-receiving window 176 of the first sleeve 170.Further, the distal end of the second sleeve, and more particularly, theelectrode edge 180 is configured for plasma ablation of a substantiallywide path in the tissue. In general, the tissue resecting device isconfigured with a tissue extraction lumen 160 having a distal endportion with a reduced cross-section that is smaller than across-section of medial and proximal portions of the lumen 160.

In one aspect of the invention, referring to FIGS. 7A-7B and 9A-9B, thetissue-extraction lumen 160 has a reduced cross-sectional area in lumenregion 190B proximate the plasma resecting tip or electrode edge 180wherein said reduced cross section is less than 95%, 90%, 85% or 80%than the cross sectional area of medial and proximal portions 190A ofthe tissue-extraction lumen, and wherein the axial length of thetissue-extraction lumen is at least 10 cm, 20 cm, 30 cm or 40 cm. In oneembodiment of tissue resecting device 100 for hysteroscopic fibroidresection and extraction (FIG. 1 ), the shaft assembly 140 of the tissueresecting device is 35 cm in length.

FIGS. 10A-10C illustrate the working end 145 of the tissue resectingdevice 100 with the reciprocating resecting sleeve or inner sleeve 175in three different axial positions relative to the tissue receivingwindow 176 in outer sleeve 170. In FIG. 10A, the resecting sleeve 175 isshown in a retracted or non-extended position in which the sleeve 175 isat it proximal limit of motion and is prepared to advance distally to anextended position to thereby electrosurgically resect tissue positionedin and/or suctioned into window 176. FIG. 10B shows the resecting sleeve175 moved and advanced distally to a partially advanced or medialposition relative to tissue resection window 176. FIG. 10C illustratesthe resecting sleeve 175 fully advanced and extended to the distal limitof its motion wherein the plasma resecting electrode 180 has extendedpast the distal end 226 of tissue-receiving window 176 at which momentthe tissue strip 225 is resected from tissue volume 220 and captured inreduced cross-sectional lumen region 190B.

Now referring to FIGS. 10A-10C and FIGS. 11A-11C, another aspect of theinvention comprises tissue displacement mechanisms provided by multipleelements and processes to displace and move tissue strips 225 in theproximal direction in lumen 160 of resecting sleeve 175 to thus ensurethat tissue does not clog the lumen of the inner sleeve 175. As can beseen in FIG. 10A and the enlarged views of FIGS. 11A-11C, one tissuedisplacement mechanism comprises a projecting element 230 that extendsproximally from distal tip 232 which is fixedly attached to outer sleeve170. The projecting element 230 extends proximally along central axis168 in a distal chamber 240 defined by outer sleeve 170 and distal tip232. In one embodiment depicted in FIG. 11A, the shaft-like projectingelement 230, in a first functional aspect, comprises a mechanical pusherthat functions to push a captured tissue strip 225 proximally from thesmall cross-section lumen 190B of resecting sleeve 175 as the sleeve 175moves to its fully advanced or extended position. In a second functionalaspect, the chamber 240 in the distal end of sleeve 170 is configured tocapture a volume of saline distending fluid 244 from the working space,and wherein the existing RF electrodes of the working end 145 arefurther configured to explosively vaporize the captured fluid 244 togenerate proximally-directed forces on tissue strips 225 resected anddisposed in lumen 160 of the resecting sleeve 175. Both of these twofunctional elements and processes (tissue displacement mechanisms) canapply substantial mechanical force to captured tissue strips 225. Forexample, the explosive vaporization of liquid in chamber 240 canfunction to move tissue strips 225 in the proximal direction in thetissue-extraction lumen 160. It has been found that using thecombination of multiple functional elements and processes can virtuallyeliminate the potential for tissue clogging the tissue extraction lumen160.

More in particular, FIGS. 12A-12C illustrate sequentially the functionalaspects of the tissue displacement mechanisms and the explosivevaporization of fluid captured in chamber 240. In FIG. 12A, thereciprocating resecting sleeve 175 is shown in a medial positionadvancing distally wherein plasma at the electrode edge 180 is resectinga tissue strip 225 that is disposed within lumen 160 of the resectingsleeve 175. In FIG. 12A-12C, it can be seen that the system operates infirst and second electrosurgical modes corresponding to thereciprocation and axial range of motion of resecting sleeve 175 relativeto the tissue-receiving window 176. As used herein, the term“electrosurgical mode” refers to which electrode of the two opposingpolarity electrodes functions as an “active electrode” and whichelectrode functions as a “return electrode”. The terms “activeelectrode” and “return electrode” are used in accordance with conventionin the art—wherein an active electrode has a smaller surface area thanthe return electrode which thus focuses RF energy density about such anactive electrode. In the working end 145 of FIGS. 10A-11C, the resectingelectrode element 195 and its electrode edge 180 must comprise theactive electrode to focus energy about the electrode to generate theplasma for tissue resection. Such a high-intensity, energetic plasma atthe electrode edge 180 is needed throughout stroke X indicated in FIGS.12A-12B to resect tissue. The first mode occurs over an axial length oftravel of inner sleeve 175 as it crosses the tissue receiving window176, at which time the entire exterior surface of outer sleeve 170comprises the return electrode indicated at 185. The electrical fieldsEF of the first RF mode are indicated schematically generally in FIG.12A.

FIG. 12B illustrates the moment in time at which the distal advancementor extension of inner resecting sleeve 175 entirely crosses thetissue-receiving window 176. At this time, the electrode sleeve 195 andits electrode edge 180 are confined within the mostly insulated-wallchamber 240 defined by the outer sleeve 170 and distal tip 232. At thismoment, the system is configured to switch to the second RF mode inwhich the electric fields EF switch from those described previously inthe first RF mode. As can be seen in FIG. 12B, in this second mode, thelimited interior surface area 250 of distal tip 232 that interfaceschamber 240 functions as an active electrode and the distal end portionof resecting sleeve 175 exposed to chamber 240 acts as a returnelectrode. In this mode, very high energy densities occur about surface250 and such a contained electric field EF can explosively and instantlyvaporize the fluid 244 captured in chamber 240. The expansion of watervapor can be dramatic and can thus apply tremendous mechanical forcesand fluid pressure on the tissue strip 225 to move the tissue strip inthe proximal direction in the tissue extraction lumen 160. FIG. 12Cillustrates such explosive or expansive vaporization of the distentionfluid 244 captured in chamber 240 and further shows the tissue strip 225being expelled in the proximal direction in the lumen 160 of innerresecting sleeve 175. In another variation, FIG. 14 further shows therelative surface areas of the active and return electrodes at theextended range of motion of the resecting sleeve 175, again illustratingthat the surface area of the non-insulated distal end surface 250 issmall compared to surface 255 of electrode sleeve which comprises thereturn electrode.

Still referring to FIGS. 12A-12C, it has been found that a single powersetting on the RF source 150 and controller 155 can be configured both(i) to create plasma at the electrode edge 180 of electrode sleeve 195to resect tissue in the first mode, and (ii) to explosively vaporize thecaptured distention fluid 244 in the second mode. Further, it has beenfound that the system can function with RF mode-switching automaticallyat suitable reciprocation rates ranging from 0.5 cycles per second to 8or 10 cycles per second. It has been found that the tissue resectingdevice described above can resect and extract tissue at the rate of from4 grams/min to 20 grams/min without any potential for tissue strips 225clogging the tissue-extraction lumen 160, depending on the diameter ofthe device. In one embodiment, a negative pressure source 125 can becoupled to the tissue-extraction lumen 160 to apply additionaltissue-extracting forces to tissue strips 225 in the system.

Of particular interest, the fluid-capture chamber 240 defined by sleeve170 and distal tip 232 can be designed to have a selected volume,exposed electrode surface area, length and geometry to optimize theexpelling forces applied to resected tissue strips 225. In oneembodiment, the diameter of the chamber is 3.175 mm and the length is5.0 mm which taking into account the projecting element 230, provides acaptured fluid volume of approximately 0.040 mL. In other variations,the captured fluid volume can range from 0.004 to 0.080 mL.

In one example, a chamber 240 with a captured liquid volume of 0.040 mLtogether with 100% conversion efficiency in an instantaneousvaporization would require 103 Joules to heat the liquid from roomtemperature to water vapor. In operation, since a Joule is a W*s, andthe system reciprocates at 3 Hz, the power required would be on theorder of 311 W for full, instantaneous conversion of the captured liquidto water vapor. A corresponding theoretical expansion of 1700 x wouldoccur in the phase transition, which would results in up to 25,000 psiinstantaneously (14.7 psi×1700), although due to losses in efficiencyand non-instantaneous expansion, the actual pressures would be less. Inany event, the pressures are substantial and can apply expelling forcessufficient to expel the captured tissue strips 225 along the length ofthe extraction channel 160 in the probe.

Referring to FIG. 12A, the interior chamber 240 can have an axial lengthfrom about 0.5 mm to 10 mm to capture a liquid volume ranging from about0.004 mL 0.01 mL. It can be understood in FIG. 12A, that the interiorwall of chamber 240 has an insulator layer 200 which thus limits theelectrode surface area 250 exposed to chamber 240. In one embodiment,the distal tip 232 is stainless steel and is welded to outer sleeve 170.The post element 248 is welded to tip 232 or machined as a featurethereof. The projecting element 230 in this embodiment is anon-conductive ceramic.

FIG. 13 shows the cross-section of the ceramic projecting element 230which is fluted, which in one embodiment has three flute elements 260 inthree corresponding axial grooves 262 in its surface. Any number offlutes, channels or the like is possible, for example from 2 to about20. The purpose of this design is to provide a significantcross-sectional area at the proximal end of the projecting element 230to push the tissue strip 225, while at the same time the three grooves262 permit the proximally-directed jetting of water vapor to impact thetissue exposed to the grooves 262. In one embodiment, the axial length Dof the projecting element 230 is configured to push tissue entirely outof the reduced cross-sectional region 190B of the electrode sleeveelement 195. In another embodiment, the volume of the chamber 240 isconfigured to capture liquid that when explosively vaporized provides agas (water vapor) volume sufficient to expand into and occupy at leastthe volume defined by a 10% of the total length of extraction channel160 in the device, at least 20% of the extraction channel 160, at least40% of the extraction channel 160, at least 60% of the extractionchannel 160, at least 80% of the extraction channel 160 or at least 100%of the extraction channel 160.

As can be understood from FIGS. 12A to 12C, the distention fluid 244 inthe working space replenishes the captured fluid in chamber 240 as theresecting sleeve 175 moves in the proximal direction or towards itsnon-extended position. Thus, when the resecting sleeve 175 again movesin the distal direction to resect tissue, the interior chamber 240 isfilled with fluid 244 which is then again contained and is thenavailable for explosive vaporization as described above when theresecting sleeve 175 closes the tissue-receiving window 176. In anotherembodiment, a one-way valve can be provided in the distal tip 232 todraw fluid directly into interior chamber 240 without the need for fluidto migrate through window 176.

FIG. 15 illustrates another variation in which the active electrodesurface area 250′ in the second mode comprises a projecting element 230with conductive regions and nonconductive regions 261 which can have theeffect of distributing the focused RF energy delivery over a pluralityof discrete regions each in contact with the captured fluid 244. Thisconfiguration can more efficiently vaporize the captured fluid volume inchamber 240. In one embodiment, the conductive regions 250′ can comprisemetal discs or washers on post 248. In other variation (not shown) theconductive regions 250′ can comprise holes, ports or pores in a ceramicmaterial 261 fixed over an electrically conductive post 248.

In another embodiment, the RF source 150 and controller 155 can beprogrammed to modulate energy delivery parameters during stroke X andstroke Y in FIGS. 12A-12C to provide the optimal energy (i) for plasmaresection with electrode edge 180, and (ii) for explosively vaporizingthe captured fluid in chamber 240.

FIGS. 16A-16B are sectional views of a working end 600 of a tissueresecting probe that is similar to previous embodiments. In FIGS. 16Aand 16B, the inner resecting member or sleeve 610 is shown in a distalportion of its stroke after resecting a tissue strip 225 captured in thewindow 612 in the outer sleeve 615 or housing as generally depicted inthe tissue resecting sequence of FIGS. 12A-12B.

FIGS. 16A-16B illustrate another aspect of the invention wherein theinner resecting sleeve 610 moves in a passageway 620 in the outer sleeve615 and in the distal portion of its stroke, a projecting or extendingelement 630 extends into the tissue extraction channel 632 in the innersleeve 610. In one variation, the cross-section of the extending element630 is configured to extend into the distal reduced cross-sectionportion 635 of the tissue extraction channel 632 and function in ascissor-like manner to push the tissue against the electrode edge 640 ofthe inner sleeve 610 as depicted in FIG. 16A. The extending element 630can have an axial length of at least 2 mm. In a variation, the extendingelement 630 has a length can ranging from 4 mm to 10 mm. The extendingelement 630 can have a length that equals at least 50% of the axiallength of the distal reduced cross-section region 635 of the extractionchannel 632.

In one variation, a method of resecting tissue comprises positioning aworking end of a tissue resecting probe against tissue and moving aresecting sleeve or member 610 carried by the probe wherein the moveableresecting member 610 interfaces with an extending element 630 carried bythe probe that extends into a channel 632 in the resecting sleeve tothereby resect tissue that is captured between the resecting member 610and the extending element 630. In such a variation, the step ofresecting tissue is accomplished by plasma formed at the distalelectrode edge 640 of the resecting member 610, with electrical fieldsEF (FIG. 16A) as described above.

In one variation, still referring to FIGS. 16A-16B, the extendingelement 630 has a tapered region 644 that tapers in the proximaldirection. In use, the tapered region helps insure that the distallymoving inner sleeve 610 is guided over the projecting element 630 evenif there is some flex in the distal portion of the outer sleeve 615 inthe region of window 612. It can be understood that distal movement ofthe inner sleeve 610 will engage the tapered region 644 of element 630if the outer sleeve is flexed in any direction and thereafter furtherdistal movement of the inner sleeve 610 over the projecting element 630will center the outer sleeve 615 relative to the inner sleeve 610.

In general, a method of resecting and extracting tissue comprisespositioning a window of a tubular resecting device against tissue, andreciprocating a resecting sleeve in forward and backward strokes acrossthe window wherein a projecting member separate from the resectingsleeve projects into a bore in the resecting sleeve during a portion ofits forward stroke to prevent flexing of the sleeve proximate thewindow.

In one embodiment shown in FIGS. 16A-16B, the extending element 630 hasa recessed region 648 therein for receiving a fluid volume. As can beseen in FIG. 16B, the extending element 630 is a dielectric material(e.g., a ceramic) with a central bore 660 for mounting the element 630over the post element 652 of metal endcap 655. The proximal surface 658of post element 652 functions as an electrode when vaporizing capturedfluid as described previously and shown in FIG. 16B. The electricalfields EF′ are shown in FIG. 16B which result in the explosivevaporization of the contained liquid. It can be seen in FIG. 16B thatmetal endcap 655 is fixed with annular weld 656 to outer sleeve 615(electrode) so that endcap 655 and its post element 652 also function asan electrode. FIG. 16B further illustrates that the working end hasinsulative layers on all surfaces of the distal annular space 660 thatreceives the inner resecting sleeve 610 to focus RF current paths in thecentral bore 650 of the projecting element 630. More in particular, theouter sleeve 615 is lined with an insulative layer 662 and the endcap655 has an annular inner insulator 664 bonded thereto.

FIGS. 17-19 illustrate a fluid management system 500 that can be usedwhen treating tissue in a body cavity, space or potential space 502(FIG. 18 ). The fluid management system 500 is depicted schematically ina hysteroscopic fibroid treatment system 510 that is adapted forresection and extraction of fibroids or other abnormal intra-uterinetissue using a hysteroscope 512 and tissue resection probe 515 that canbe similar to those described above. FIG. 17 depicts the probe 515 withhandle 516 and extension member 518 with working end 520 (FIG. 18 ) thatcan be introduced through working channel 522 extending through the body523 and shaft 524 of the hysteroscope 512. FIG. 17 further shows a motor525 in handle 516 of the probe that is coupled to a controller 545 andpower supply by power cable 526. FIG. 18 illustrates the working end 520of the resecting probe in a uterine cavity proximate a targeted fibroid530.

Referring to FIGS. 17-18 , in general, the fluid management system 500comprises a fluid source or reservoir 535 of a distention fluid 244, acontroller and pump system to provide fluid inflows and outflows adaptedto maintain distension of a body space and a filter system 540 forfiltering distention fluid 244 that is removed from the body cavity andthereafter returned to the fluid source 535. The use of a recovered andfiltered fluid 244 and the replenishment of the fluid source 535 isadvantageous because (i) the closed-loop fluid management system caneffectively measure fluid deficit to thereby monitor intravasation andinsure patient safety, (ii) the system can be set up and operated in avery time-efficient manner, and (iii) the system can be compact and lessexpensive to thereby assist in enabling office-based procedures.

The fluid management system 500 (FIG. 17 ) includes a computer controlsystem that is integrated with the RF control system in an integratedcontroller 545. The controller 545 is adapted to control first andsecond peristaltic pumps 546A and 546B for providing inflows andoutflows of a distention fluid 244, such as saline solution, from source535 for the purpose of distending the body cavity and controlling theintra-cavity pressure during a tissue resecting and extracting procedureas depicted in FIG. 18 . In one embodiment shown in FIGS. 17-19 , thecontroller 545 controls peristaltic pump 546A to provide positivepressure at the outflow side 548 of the pump (FIG. 17 ) to provideinflows of distention fluid 244 through first flow line 550 which is incommunication with fitting 561 and fluid flow channel 108 a inhysteroscope 515. The flow channel 108 a is described above in aprevious embodiment and is illustrated in FIG. 3 above. The controller545 further controls the second peristaltic pump 546B to providenegative pressure at the inflow side 552 of the pump (FIG. 18 ) to thesecond line 555 to assist in providing outflows of distention fluid 244from the body cavity 502. As described above, the explosive vaporizationof fluid in the working end 525 of probe 515 functions to expel tissuestrips 225 proximally in the extraction channel 160 of resecting sleeve175, which can operate in conjunction with negative pressures in line555 provided by pump 546B. In operation, the second peristaltic pump546B also operates to provide positive pressure on the outflow side 556of pump 546B in the second flow line portion 555′ to pump outflows ofdistention fluid 244 through the filter system 540 and back to the fluidsource 535.

In one system embodiment, the controller 545 operates to controlpressure in cavity 502 by pressure signals from a disposable pressuresensor 560 that is coupled to a fitting 562 in hysterocope 512 whichcommunicates with a flow channel 108 b (see FIG. 17 ) that extendsthrough the hysteroscope. The pressure sensor 560 is operatively coupledto controller 545 by cable 564. In one embodiment, the flow channel 108b has a diameter of at least 1.0 mm to allow highly accurate sensing ofactual intra-cavity pressure. In prior art commercially-available fluidmanagement systems, the intra-cavity pressure is typically estimated byvarious calculations using known flow rates through a pump or remotepressure sensors in the fluid inflow line that can measure backpressures. Such prior art fluid management systems are stand-alonesystems and are adapted for use with a wide variety of hysteroscopes andendoscopes, most of which do not have a dedicated flow channel forcommunicating with a pressure sensor. For this reason, prior art fluidmanagement systems rely on algorithms and calculations to estimateintra-cavity pressure.

The fluid channel or sensor channel 108 b used by the pressure sensor560 is independent of flow channel 108 a used for distention fluidinflows into the body cavity. In the absence of fluid flows in thesensor channel 108 b, the fluid in the channel 108 b then forms a staticcolumn of incompressible fluid that changes in pressure as the pressurein the body cavity changes. With a sensor channel cross-section of 1 mmor more, the pressure within the pressure channel column and thepressure in the body cavity are equivalent. Thus, the pressure sensor560 is capable of a direct measurement of pressure within the bodycavity.

FIG. 18 schematically illustrates the fluid management system 500 inoperation. The uterine cavity 502 is a potential space and needs to bedistended to allow for hysteroscopic viewing. A selected pressure can beset in the controller 545, for example via a touch screen 565, which thephysician knows from experience is suited for distending the cavity 502and/or for performing a procedure. In one embodiment, the selectedpressure can be any pressure between 0 and 150 mm Hg. In one systemembodiment, the first pump 546A can operate as a variable speed pumpthat is actuated to provide a flow rate of up to 850 ml/min throughfirst line 550. In this embodiment, the second pump 546B can operate ata fixed speed to move fluid in the second line 555. In use, thecontroller 545 can operate the pumps 546A and 546B at selected matchingor non-matching speeds to increase, decrease or maintain the volume ofdistention fluid 244 in the uterine cavity 502. Thus, by independentcontrol of the pumping rates of the first and second peristaltic pumps546A and 546B, a selected set pressure in the body cavity can beachieved and maintained in response to signals of actual intra-cavitypressure provided by sensor 560.

In one system embodiment, as shown in FIGS. 18-19 , the fluid managementsystem 500 includes a filter module or system 540 that can include afirst filter or tissue-capturing filter 570 that is adapted to catchtissue strips 225 that have been resected and extracted from the bodycavity 502. A second filter or molecular filter 575, typically a hollowfiber filter, is provided beyond the first filter 570, wherein themolecular filter 575 is adapted to remove blood and other body materialsfrom the distention fluid 244. In particular, the molecular filter 575is capable of removing red blood cells, hemoglobin, particulate matter,proteins, bacteria, viruses and the like from the distention fluid 244so that endoscopic viewing of the body cavity is not obscured or cloudedby any such blood components or other contaminants. As can be understoodfrom FIGS. 16-18 , the second peristaltic pump 546B at its outflow side556 provides a positive pressure relative to fluid flows into the filtermodule 540 to move the distention fluid 244 and body media through thefirst and second filters, 570 and 575, and in a circulatory flow back tothe fluid source 535.

Referring to FIG. 19 , in an embodiment, the first filter 570 comprisesa container portion or vial 576 with a removable cap 577. The inflow ofdistention fluid 244 and body media flows though line portion 555 andthrough fitting 578 into a mesh sac or perforate structure 580 disposedin the interior chamber 582 of the vial 576. The pore size of theperforate structure 580 can range from about 200 microns to 10 microns.The lumen diameter of hollow fibers 585 in the second filter 575 can befrom about 400 microns to 20 microns. In general, the pore size ofperforate structure 580 in the first filter 570 is less than thediameter of the lumens of hollow fibers 585 in the second filter 575. Inone embodiment, the pore size of the perforate structure 580 is 100microns, and the lumen size of the hollow fibers 585 in the molecularfilter 575 is 200 microns. In one embodiment, the molecular filter 575is a Nephros DSU filter available from Nephros, Inc., 41 Grand Ave.,River Edge, N.J. 07661. In one variation, the filter 575 is configuredwith hollow fibers having a nominal molecular weight limit (NMWL) ofless than 50 kDa, 30 kDa or 20 kDa.

Referring to FIG. 19 , it can be seen that the filter module 540includes detachable connections between the various fluid flow lines toallow for rapid coupling and de-coupling of the filters and flow lines.More in particular, flow line 555 extending from the tissue resectingprobe 515 has a connector portion 592 that connects to inlet fitting 578in the first filter 570. Flow line portion 555′ that is intermediate thefilters 570 and 575 has connector portion 596 a that connects to outletfitting 596 b in first filter 570. The outflow end of flow line 555′ hasconnector 598 a that connects to inlet fitting 598 b of the secondfilter 575. The portion 590 of the second flow line 555 that isintermediate the second filter 575 and fluid source 535 has connectorportion 602 a that connects to outlet fitting 602 b in the second filter575. In one embodiment, at least one check valve 605 is provided in theflow path intermediate the filters 570, 575 which for example can be inline 555′, connectors 596 a, 598 a or fittings 596 b, 598 b. In FIG. 19, a check valve 605 is integrated with the inlet end 608 of the secondfilter 575. In use, the operation of the system will result insubstantial fluid pressures in the interior of the second filter, andthe check valve 605 allows for de-coupling the first filter withoutescape of pressure and release of fluid media into the environment, forexample, when the tissue resection procedure is completed and thephysician or nurse wishes to transport the vial 576 and tissue strips225 therein to a different site for biopsy purposes.

In one aspect, a fluid management system comprising a first fluid line550 configured to carry distention fluid 224 or influent from a fluidsource 535 to a body space, a second fluid line 555, 555′ and 560configured to carry fluid from the body space to a first filter 570 andthen to a second filter 575 and then back to the fluid source 535, apump operatively coupled to the second fluid line to move the fluid andat least one check valve 605 in the second fluid line intermediate thefirst and second filters 570 and 575.

In one embodiment, the controller 545 of the fluid management system 500is configured for calculation of a fluid deficit that is measured as adifference between a fluid volume delivered to the body space 502 and afluid volume recovered from the body space during a medical proceduresuch as fibroid removal (see FIGS. 17-18 ). A method of fluid managementin a hysteroscopic procedure comprises providing a distention fluidsource 535 (FIG. 18 ) having a predetermined volume, introducing fluid(e.g., saline) from the source 535 through a first flow path or line 550into the uterine cavity and through a second flow line 555 out of thecavity into a filter module 540 and through a further portion 590 of thesecond flow line back to the fluid source 535 wherein the interiorvolume of the first and second flow lines and the filter module whensubtracted from the predetermined volume of the source 535 equals 2.5liters or less to thereby insure that saline intravasion is less than2.5 liters. In this variation, the predetermined volume of the source535 can be 3.0 liters, as in a standard 3 liter saline bag, and theinterior system volume can be at least 0.5 liters. In one variation, thefluid management system 500 can include a sensor system for determiningthe volume of fluid remaining in the source 535, and the sensor canprovide a signal to the controller 545 which in turn can provide avisual or aural signal relating to remaining fluid volume in fluidsource 535. In one variation, the fluid source 535 can be a bag thathangs from a member including a load cell 625 (FIGS. 17, 19 ) which isconfigured to send load signals to the controller 545. The controllercan have a screen 565 which continuously displays a fluid parameter suchas calculated fluid deficit or fluid remaining in the source 535. Inother variations, the sensor adapted for sensing the weight or volume offluid in the fluid source can be a float or level sensor in a fluidcontainer, an impedance or capacitance sensor coupled to the fluidsource container, an optical sensor operatively coupled to the fluidcontainer or any other suitable type of weight or volume sensingmechanism. Any such sensor system can send signals to the controller forproviding fluid deficit calculations or fluid intravasation warnings.

While certain embodiments of the present invention have been describedabove in detail, it will be understood that this description is merelyfor purposes of illustration and the above description of the inventionis not exhaustive. Specific features of the invention are shown in somedrawings and not in others, and this is for convenience only and anyfeature may be combined with another in accordance with the invention. Anumber of variations and alternatives will be apparent to one havingordinary skills in the art. Such alternatives and variations areintended to be included within the scope of the claims. Particularfeatures that are presented in dependent claims can be combined and fallwithin the scope of the invention. The invention also encompassesembodiments as if dependent claims were alternatively written in amultiple dependent claim format with reference to other independentclaims.

What is claimed is:
 1. A tissue resecting device, comprising: a tubularouter sleeve having a lumen extending axially therethrough; a conductiveend cap disposed across a distal end of the lumen, the conductive endcap including a post element extending proximally therefrom; adielectric extending element having a central bore formed therein, theextending element being mounted on the post element; and a tubular innersleeve slidably disposed within the lumen of the outer sleeve andconfigured to move between a proximal position and a distal position,the inner sleeve including a distal electrode edge and an extractionlumen extending therethrough; wherein the extending element includes aproximally tapered outer surface configured to extend into the innersleeve as the inner sleeve moves toward the distal position.
 2. Thetissue resecting device of claim 1, wherein the tubular outer sleeveincludes a conductive outer surface and a non-conductive coatingdisposed along an inner surface of the tubular outer sleeve.
 3. Thetissue resecting device of claim 1, wherein the tubular inner sleeveincludes a conductive inner surface and a non-conductive coatingdisposed along an outer surface of the tubular inner sleeve.
 4. Thetissue resecting device of claim 1, wherein the proximally tapered outersurface centers the inner sleeve relative to the outer sleeve as theinner sleeve is advanced distally over the extending element.
 5. Thetissue resecting device of claim 1, wherein a distal end of theextending element abuts a proximal surface of the conductive end cap. 6.The tissue resecting device of claim 5, further including an annularinsulator bonded to the proximal surface of the conductive end cap aboutthe extending element.
 7. The tissue resecting device of claim 1,wherein a proximal surface of the post element is exposed to theextraction lumen within the central bore when the inner sleeve is in thedistal position.
 8. The tissue resecting device of claim 1, wherein aproximal surface of the post element and the central bore define arecessed region within the extending element configured to receive afluid volume therein.
 9. A tissue resecting device, comprising: atubular outer sleeve having a lumen extending axially therethrough, theouter sleeve including a tissue-receiving window formed through a wallthereof; a conductive end cap disposed across a distal end of the lumen,the conductive end cap including a post element extending proximallytherefrom; a dielectric extending element having a central bore formedtherein, the extending element being mounted on the post element suchthat a proximal surface of the post element is exposed; a tubular innersleeve slidably disposed within the lumen of the outer sleeve andconfigured to move between a proximal position and a distal position,the inner sleeve including a distal electrode edge and an extractionlumen extending therethrough; and a controller configured to operate thetissue resecting device in a first electrosurgical mode when the distalelectrode edge is axially disposed between a proximal end of thetissue-receiving window and a distal end of the tissue-receiving window,and in a second electrosurgical mode when the distal electrode edge isdisposed distally of the distal end of the tissue receiving window. 10.The tissue resecting device of claim 9, wherein the conductive end capis spaced apart distally from the tissue receiving window.
 11. Thetissue resecting device of claim 9, wherein the extending elementincludes a proximally tapered outer surface configured to extend intothe inner sleeve as the inner sleeve moves toward the distal position.12. The tissue resecting device of claim 9, wherein in the firstelectrosurgical mode, RF energy forms a first electric field between thedistal electrode edge and an outer surface of the outer sleeve therebyforming a plasma at the distal electrode edge.
 13. The tissue resectingdevice of claim 9, wherein in the second electrosurgical mode, RF energyforms a second electric field between the proximal surface of the postelement and an inner surface of the inner sleeve thereby causingexplosive vaporization of a fluid volume disposed within the centralbore proximal of the post element.
 14. The tissue resecting device ofclaim 9, wherein an inner surface of the outer sleeve includes anon-conductive coating.
 15. The tissue resecting device of claim 9,wherein an outer surface of the inner sleeve proximal of the distalelectrode edge includes a non-conductive coating.
 16. The tissueresecting device of claim 9, wherein a distal end of the extendingelement mates against a proximal face of the conductive end cap.
 17. Thetissue resecting device of claim 16, wherein the metal conductive endcap includes an annular insulator bonded to the proximal face andextending radially outward from the extending element such that none ofthe proximal face is exposed within the lumen of the outer sleeve. 18.The tissue resecting device of claim 9, wherein the extending elementhas a symmetrical cross-sectional shape relative to a centrallongitudinal axis of the outer sleeve.
 19. The tissue resecting deviceof claim 9, wherein the extending element comprises a ceramic material.20. A tissue resecting device, comprising: a conductive tubular outersleeve having a lumen extending axially therethrough, a tissue-receivingwindow formed through a wall thereof, and a non-conductive coatingextending along an inner surface thereof; a conductive end cap disposedacross a distal end of the lumen, the end cap including a conductivepost element extending proximally from a proximal face of the end cap; anon-conductive extending element having a central bore formed therein,the extending element being mounted on the post element such that aproximal surface of the post element is exposed within the central bore;a conductive tubular inner sleeve slidably disposed within the lumen ofthe outer sleeve and configured to move between a proximal position anda distal position, the inner sleeve including a distal electrode, anextraction lumen extending therethrough, and a non-conductive coatingextending proximally from the distal electrode along an outer surface ofthe inner sleeve; and a controller configured to operate the tissueresecting device in a first electrosurgical mode when a distal edge ofthe distal electrode is disposed proximal of a distal end of thetissue-receiving window, and in a second electrosurgical mode when thedistal edge is disposed distally of the distal end of the tissuereceiving window; wherein in the first electrosurgical mode, RF energyforms an electric field between the distal edge and an outer surface ofthe outer sleeve, thereby forming plasma at the distal edge forresecting tissue extending into the tissue-receiving window as the innersleeve is advanced distally toward the distal position; wherein in thesecond electrosurgical mode, RF energy forms an electric field betweenthe proximal surface of the post element and an inner surface of theinner sleeve, thereby vaporizing fluid disposed within the central boreto force tissue resected by the plasma proximally within the extractionlumen.